U.S. patent number 4,791,833 [Application Number 07/068,755] was granted by the patent office on 1988-12-20 for reduction gear mechanism for motor-driven drill incorporating speed changing mechanism.
This patent grant is currently assigned to Japan Storage Battery Co., Ltd.. Invention is credited to Yasuharu Sakai, Shinichi Segawa, Tadashi Yasui.
United States Patent |
4,791,833 |
Sakai , et al. |
December 20, 1988 |
Reduction gear mechanism for motor-driven drill incorporating speed
changing mechanism
Abstract
A reduction gear mechanism, incorporating a speed changing
mechanism, for use with a motor-driven drill. The mechanism
includes at least one planetary speed reducer having a sun gear to
which rotation of an electric motor is transmitted, a plurality of
planet gears arranged around the sun gear and engaged with the sun
gear, an internal gear internally engaged with the planet gears,
and a planet gear holding plate which pivotally supports the planet
gears on one side of it and has an output shaft on the other side
of it. The internal gear of at least one planetary speed reducer
includes a cylindrical internal gear. The reduction gear includes
mechanisms for locking the cylindrical internal gear to prevent
rotation of the cylindrical internal gear and for engaging the
cylindrical internal gear with the planet gear holding plate so
that the cylindrical internal gear and the planet gear holding
plate rotate as a single unit.
Inventors: |
Sakai; Yasuharu (Kyoto,
JP), Segawa; Shinichi (Kyoto, JP), Yasui;
Tadashi (Kyoto, JP) |
Assignee: |
Japan Storage Battery Co., Ltd.
(Kyoto, JP)
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Family
ID: |
26478542 |
Appl.
No.: |
07/068,755 |
Filed: |
June 30, 1987 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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754489 |
Jul 12, 1985 |
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Foreign Application Priority Data
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Jul 16, 1984 [JP] |
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59-148291 |
Oct 11, 1984 [JP] |
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59-213225 |
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Current U.S.
Class: |
475/299;
475/320 |
Current CPC
Class: |
B25F
5/001 (20130101); F16H 3/54 (20130101); F16H
3/64 (20130101); F16H 35/10 (20130101); H02K
7/116 (20130101) |
Current International
Class: |
B25F
5/00 (20060101); F16H 3/64 (20060101); F16H
3/54 (20060101); F16H 35/00 (20060101); F16H
35/10 (20060101); F16H 3/44 (20060101); H02K
7/116 (20060101); F16H 003/44 () |
Field of
Search: |
;74/785,768,769,342,343
;310/83 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1072143 |
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Sep 1954 |
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FR |
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2102515 |
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Feb 1983 |
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GB |
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Primary Examiner: Wright; Dirk
Assistant Examiner: Macris; Harold F.
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak &
Seas
Parent Case Text
This is a continuation of application Ser. No. 754,489, filed July
12, 1985, now abandoned.
Claims
We claim:
1. In a reduction gear mechanism with a speed changing mechanism
for a motor-driven drill including a gear case, at least one
planetary speed reducer comprising a sun gear to which rotation of
an electric motor is transmitted, a plurality of planet gears
arranged around said sun gear and engaged with said sun gears, an
internal gear internally engaged with said planet gear, and a
planet gear holding plate which rotatably supports said planet
gears on one side thereof and has an output shaft on the other side
thereof, the improvement wherein:
said internal gear of at least one planetary speed reducer
comprises a slidably mounted cylindrical internal gear, said
cylindrical gears comprising a set of internal gear teeth engaged
with said planet gear and a set of outer gear teeth, an annular
groove being formed in an outer surface of said internal gear;
said planet gear holding plate has a set of gear teeth engaged with
said internal gear teeth of said internal gear in a first position
of said internal gear to allow said internal gear to rotate with
said planet gear holding plate;
a separate set of fixed teeth is fixed to a structure within which
said sun gear rotates, and said set of outer gear teeth of said
internal gear is engaged in a second position of said internal gear
with said fixed teeth to rotatably lock said internal gear,
and wherein there is provided a lever for sliding said internal
gear between said first and second position, said lever extending
in a semicircle around said internal gear, said gear case extending
circumferentially around said internal gear, said lever being
pivotally mounted to said gear case, and said lever having pins on
opposite sides thereof passing through windows in said gear case
and slidably received in said annular groove at opposed points
around the circumference of said internal gear.
2. The reduction gear as claimed in claim 1, wherein said separate
set of fixed teeth is provided on a second internal gear, said
second internal gear being fixed to said gear case.
3. The reduction gear as claimed in claim 1, wherein said at least
one planetary speed reducer comprises a multistage planetary speed
reducer, said output shaft of said planet gear holding plate
comprising a sun gear engaged with planet gears of a following
stage.
4. In a reduction gear mechanism with a speed changing mechanism
for a motor-driven drill including a gear case, at least one
planetary speed reducer comprising a sun gear to which rotation of
an electric motor is transmitted, a plurality of planet gears
arranged around said sun gear and engaged with said sun gear, an
internal gear internally engaged with said planet gear, and a
planet gear holding plate which rotatably supports said planet
gears on one side thereof and has an output shaft of the other side
thereof, the improvement wherein:
a ring board is arranged between said cylindrical internal gear and
an end wall of said gear case, said ring board rotatable and
movable along said gear axis, said right board having arms on one
side extendable through through-holes formed in said cylindrical
internal gear to cuts formed in said planet gear holding plate and
a stop on the other side of said ring board which is engageable
with a groove formed in a wall of said gear case;
a slide lever is provided for moving said ring board, said lever
being inserted into a window formed in said gear case, said lever
being slidably engageable with said cuts and said groove; and
said planetary speed reducer comprises a multi-stage planetary
speed reducer, said output shaft of said planet gear holding plate
comprising a sun gear engaged with planet gears of a following
stage,
wherein, when said ring board is moved towards said cylindrical
internal gear, said cylindrical internal gear is engaged with said
planet gear holding plate through said arms of said ring board so
that said cylindrical internal gear and said planet gear holding
plate are rotated as one unit, and when said ring board is moved
towards said end wall of said gear case, said cylindrical internal
gear and said planet gear holding plate are disengaged from one
another, and said stop is engaged with said groove formed in said
end wall of said gear case so that said ring board and said
cylindrical internal gear are locked, whereby rotation of said ring
board and said internal gear is prevented.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a reduction gear with a speed
changing mechanism used for a motor-driven driven drill.
A planetary speed reducing mechanism is extensively employed as a
speed reducing mechanism for a motor-driven drill because it is
relatively simple in construction and has input and output shafts
located on the same axis. However, the planetary speed reducing
mechanism is disadvantages in that it is inherently difficult to
incorporate a speed changing system within the planetary mechanism,
and accordingly it is necessary to provide a speed changing
mechanism in addition to the planetary speed reducing mechanism,
with the result that the power transmission mechanism is
necessarily intricate.
SUMMARY OF THE INVENTION
Overcoming these difficulties, in accordance with the invention, a
speed changing mechanism is included in a planetary speed reducing
mechanism without impairing the function of the latter. More
specifically, a reduction gear mechanism provided by the invention
comprises a sun gear to which rotation of an electric motor is
transmitted, a plurality of planet gears engaged with the sun gear,
a cylindrical internal gear engaged with the planet gears, and a
planet gear holding plate which pivotally supports the planet gears
on one side and has the output shaft on the other side, and further
including means for locking the cylindrical internal gear to
prevent rotation of the latter, and means for rotatably engaging
the cylindrical internal gear with the planet gear holding plate.
Furthermore, the reduction gear may be modified by arranging a
plurality of such planetary speed reducers coupled in series, with
at least one of the speed reducers having the above-described
functions.
The means for locking the internal gear to prevent the rotation of
the latter and the means for engaging the internal gear with the
planet gear holding plate are employed to slide the internal gear
along the gear axis. For this purpose, engaging teeth are formed on
the planet gear holding plate, the internal gear, and the gear
case.
When, in the reduction gear mechanism of the invention thus
constructed, the internal gear is slid towards the end wall of the
gear case, the internal teeth or engaging teeth of the internal
gear are disengaged from the engaging teeth of the planet gear
holding plate and then engaged with the engaging teeth of the gear
case so that the internal gear is locked, and the original
functions of the planetary speed reducing mechanism are performed.
That is, as the sun gear is rotated, the planet gears, being
engaged with the sun gear, are rotated and revolved along the
internal teeth of the internal gear. Since the planet gears are
pivotally supported by the planet gear holding plate, the
revolution of the planet gears is transmitted to the planet gear
holding plate so that a rotational output is provided at the output
shaft of the holding plate in the following reduction gear
ratio:
When the internal gear is moved towards the planet gear holding
plate, the internal gear is disengaged from the gear case, while
the internal teeth or engaging teeth of the internal gear are
engaged with the engaging teeth of the planet gear holding plate.
As a result, the internal gear, the planet gears, and the planet
gear holding plate are joined together, and therefore no revolution
of the planet gears along the internal gear occurs. Accordingly,
the planet gears are not rotated, and the sun gear rotates the
internal gear and the planet gear holding plate as a single unit.
That is, the reduction gear is inoperative, and the rotation of the
sun gear is directly transmitted to the output shaft provided on
the planet gear holding plate.
In other words, the reduction gear can perform two actions: (1)
when the internal gear is locked with respect to the gear case, the
reduction gear operates as an ordinary planetary speed reducing
mechanism, and (2) when the internal gear is disengaged from the
gear case and engaged with the planet gear holding plate, the input
rotation is outputted directly, that is, the input and output
rotational speeds are the same.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view showing a first embodiment of a reducing
gear mechanism according to this invention;
FIG. 2 is a perspective view, with parts cut away, showing an
example of a cylindrical internal gear sliding arrangement in the
device of the invention;
FIG. 3 is a sectional view of the arrangement shown in FIG. 2;
FIG. 4 shows a second embodiment of a reducing gear mechanism
according to the invention; and
FIG. 5 is a sectional view taken along a line A--A in FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a sectional view showing an example of a reduction gear
mechanism construction according to the invention. In this example,
three planetary speed reducing mechanisms are provided, and a speed
changing mechanism of the invention is employed in a second of the
planetary speed reducing mechanisms.
In FIG. 1, reference numeral 1 designates a gear case. A motor 3 is
mounted on the outer surface of one end of the case 1 through a
mounting fixture 2. Reference numeral 4 designates a bearing, which
also serves as the end wall of the gear case 1 as well as rotatably
supporting the output shaft 5, the bearing 4 being engaged with and
fixedly secured to the case 1 with screws; 6, an outer case in
which the motor 3 and the speed reducer case 1 are mounted; and 7,
a cover surrounding the bearing 4. The cover 7 is rotatably mounted
on the rear end of the bearing 4 through a washer 8, which serves
also as a retainer for the output shaft 5, so that the cover 7 can
be used as a knob for adjusting the elastic pressure of a ball
clutch (described below).
As described above, the three planetary speed reducing mechanisms
are accommodated within the case 1. In FIG. 1, reference numeral 11
designates a sun gear rotationally fixed on the output shaft 3a of
the motor 3; and 12, a plurality of planet gears engaged with the
sun gear 11, the planet gears 12 rotatably mounted on shafts
extending from a planet gear holding plate 14. The other end
portion of the planet gear holding plate 14 is formed into a sun
gear 21 for the next planetary speed reducing mechanism. A
cylindrical internal gear 13 is engaged with the planet gears 12.
In the case of the mechanism of FIG. 1, in order to reduce the
total number of components, the cylindrical internal gear 13 is
mounted in the gear case 1. The above-described components 1
through 14 form the first stage of the planetary speed reducing
mechanism.
The second stage of the planetary speed reducing mechanism includes
the aforementioned sun gear 21 (which is a part of the planet gear
holding plate 14), a plurality of planet gears 22 engaged with the
sun gear 21, a planet gear holding plate 24 pivotally supporting
the planet gears 22, and a cylindrical internal gear 23 engaged
with the planet gears 22. Engaging teeth 23b are formed in the
outer wall of the cylindrical internal gear 23. The cylindrical
internal gear 23 is rotatably arranged in the gear case 1 and is
slidable along the axis of the gear (horizontally in FIG. 1).
Engaging teeth 24a and 1a, engageable with the internal gear 23,
are formed in the outer wall of the planet gear holding plate 24
and in the part of the inner wall of the gear case 1 closer to its
end face, respectively. Further in FIG. 1, reference numeral 25
designates a slide lever for sliding the aforementioned cylindrical
internal gear 23 in the axial direction of the gear. The operating
lever 25a of the slide lever 25 is slidably engaged with an annular
groove 23c formed in the middle of the outer wall of the
cylindrical internal gear 23. By sliding the slide lever 25 along
the gear axis, the cylindrical internal gear 23 can be selectively
moved towards the planet gear holding plate 24 (to the position
shown in FIG. 1) or towards the end face of the gear case.
The third stage of the planetary speed reducing mechanism includes
a sun gear 31 formed integrally with the planet gear holding plate
24 of the second planetary speed reducing mechanism, planet gears
32 engaged with the sun gear 31, a planet gear holding plate 34
pivotally supporting the planet gears 32, and a cylindrical
internal gear 33 engaged with the planet gears 32. The output shaft
5 is connected to the planet gear holding plate 34 to transmit
torque.
The cylindrical internal gear 33 is rotatably mounted in the gear
case 1. The rear end face 33a of the internal gear 33 is protruded,
and steel balls 10 are abutted against the rear end face by a
coiled spring 9, thus forming a ball clutch. When a rotational
moment larger than a predetermined value is applied to the output
shaft 5, the steel balls 10 are pushed back by the protruding rear
end face 33a of the cylindrical internal gear 33 so that the latter
idles to prevent application of an excessively large load to the
motor. A cam formed in the inner wall of the aforementioned cover 7
is engaged with a retainer for the coiled spring 9. The cover 7 is
turned to move the retainer back and forth to adjust the
compression of the coiled spring 9 to thereby adjust the elastic
pressure of the ball clutch.
In the device of the invention constructed as described above, when
the slide lever 25 is moved towards the motor 3, the second
cylindrical internal gear 23 coupled to the slide lever 25 is moved
towards the end face of the gear case 1. As a result, the engaging
teeth 23b formed in the outer wall of the cylindrical internal gear
23 are engaged with the engaging teeth 1a formed in the inner wall
of the gear case 1, that is, the cylindrical internal gear 23 and
the gear case 1 rotate together, and thus the operation of an
ordinary planetary speed reducing mechanism is performed. In other
words, the torque reduced by the first planetary speed reducing
mechanism rotates the second sun gear 21, thereby to rotate the
planet gears 22. Being internally engaged with the cylindrical
internal gear 23, the planet gears 22 revolve in the direction of
input rotation along with the cylindrical internal gear (planetary
motion) to rotate the planet gear holding plate 24 at a reduced
speed, the rotation of the latter being transmitted to the third
speed reducing mechanism.
If the slide lever 25 is moved towards the output shaft 5, the
cylindrical internal gear is disengaged from the gear case 1,
whereupon the cylindrical internal gear 23 is engaged with the
planet gear holding plate 24 having engaging gears 24a on its outer
wall so that the former is made rotationally integral with the
latter. Therefore, the rotation and revolution of the planet gears
are stopped, that is, the sun gear 21 is directly coupled to the
planet gear holding plate 24. Accordingly, in this case, the planet
gear holding plate 24 does not function as a part of the speed
reducer but transmits the torque of the sun gear 21 to the
following stage directly.
In the above-described embodiment, the engaging teeth of the
internal gear which selectively engage with the second planet gear
holding plate 24 are the internal teeth 23a, and the engaging teeth
23b formed in the outer wall are selectively engaged with the gear
case 1. However, it should be noted that all that is necessary for
the engaging teeth is to engage with the internal gear, and
therefore the engaging teeth are not limited in position and in
configuration.
FIGS. 2 and 3 show an example of an arrangement for sliding the
cylindrical internal gear 23. More specifically, FIG. 2 is a
perspective view, with parts cut away, showing parts of the gear
case 1 and the cylindrical internal gear 23, and FIG. 3 is a
sectional view of the same. As shown in these figures, an annular
groove 23c is formed in the outer wall of the cylindrical internal
gear 23, and both ends of the lever 25, having fulcrums 1c on the
gear case, are inserted into windows 16 formed in the gear case 1
so that the ends are slidably engaged with the annular groove 23c.
Therefore, the cylindrical internal gear can be moved along the
gear axis by operating the lever 25.
EMBODIMENT 2
FIG. 4 is a sectional view showing another example of a reduction
gear mechanism of the invention, and FIG. 5 is a sectional view
taken along a line A--A in FIG. 4. In this example, two planet gear
speed reducing mechanisms are arranged in series, and the mechanism
of the invention is employed in the first planet gear speed
reducing mechanism.
In this example, a rotatable ring board 35 is arranged between an
internal gear 13 and one end of a gear case 1, and the ring board
35 thus arranged is operated to lock the cylindrical internal gear
13 or to cause the latter to engage a planet gear holding plate 14.
In FIGS. 4 and 5, reference numeral 35 designates the ring board
arranged between the end face of the internal gear 13 and the end
of the gear case 1. The ring board 35 has a stop 35a which is
fitted in a groove 1d formed in the gear case 1. Further, the ring
board 35 has arms 35b on the side thereof opposite the side where
the stop 35a is provided. When the ring board 35 is moved toward
the internal gear 13, the arms 35b reach cuts 14a of the planet
gear holding plate 14 through through-holes 13a formed in the
peripheral portion of the internal gear 13. Further in FIGS. 4 and
5, reference numeral 25 designates a slide lever which is
externally slid to move the ring board 25 between the end of the
gear case 1 and the internal gear 13.
In the two-stage planet gear speed reducing device thus
constructed, when the stop 35a of the ring board 35 is fitted in
the groove 1d at the end wall of the gear case 1, the internal gear
13 is secured to the gear case 1 through the stop 35a and the arms
35b of the ring board. Therefore, the rotation of the motor 3 is
transmitted through a sun gear 11 to planet gears 12. As a result,
the planet gears 12 are rotated and revolved as they are engaged
with the internal gear 13 (planet motion), and thus the planet gear
holding plate 14 pivotally supporting the planet gears 12 is
rotated with the reduction gear ratio and the rotation of the
planet gear holding plate 14 is transmitted to the following speed
reducing mechanism. When, on the other hand, the slide lever 25 is
moved in the opposite direction to move the ring board 35 towards
the internal gear 13, the stop 35a of the ring board is disengaged
from the groove 1d of the gear case 1 and the arms 35b of the ring
board are inserted into the cuts 14a of the planet gear holding
plate 14 through the through-holes 13a formed in the peripheral
portion of the internal gear 13, and thus the internal gear 13 is
coupled through the arms 35a to the planet gear holding plate 14.
Therefore, the revolution of the planet gears 12 is stopped; that
is, the planet gears 12 cannot rotate. Accordingly, the sun gear
11, the planet gears, and the internal gear 12 rotate as a single
unit in the gear case 1 so that an output shaft 14b, which is
provided on the planet gear holding plate 14 to drive the following
stage, is rotated at the same speed as the motor 3.
As is apparent form the above description, in the reducing gear
device of the invention, the gear case, the cylindrical internal
gear, and the planet gear holding plate are related to one another
as follows: When the cylindrical internal gear is rotationally
engaged with the gear case, the device serves as an ordinary
reduction gear. When the cylindrical internal gear is disengaged
from the gear case and rotated with the planet gear holding plate,
the input sun gear, the planet gears, and the planet gear holding
plate act as a single rotary unit; that is, the device does not
function as a reduction gear. Therefore, the speed of the planetary
reduction gear can be changed with a considerably simple mechanism.
This greatly contributes to a reduction of the size, weight and
cost of a motor-driven drill.
* * * * *